This invention relates to rolls in general and more particularly to an improved roll of the type referred to as a "floating roll".
A floating roll is a roll comprising a rotating shell forming the working roll periphery and a fixed beam extending longitudinally through the shell and leaving an annular space between it and the shell periphery, the ends of the beam projecting from the shell and being adapted to receive external forces and the shell bearing on the beam via a pressure fluid in a longitudinal chamber having a supply pipe and formed in the space between the shell and beam, the chamber being divided by a sealing system mounted on the beam and comprising strip-like longitudinal seals extending along the beam and shell on both sides of the operating plane of the roll and transverse end seals disposed on the opposite ends of the chamber. Rolls of this kind, with various embodiments of the longitudinal and transverse end seals, are described in German Patent Specification Nos. 11 93 739, 20 25 777 and 27 18 414.
In German PS No. 11 93 739, the longitudinal seals are strips having a substantially L-shaped cross-section, the short arm of the "L" bearing against the inner surface of the roll shell and the long arm of the "L" engaging and bearing in a groove, undercut at one side, in the beam. The pressure acts from the "outside" of the "L" on the sealing strip and tilts it around the bearing point at the free end of the long arm, thus pressing it against the inner periphery of the roll shell. German patent specification Nos. 20 25 777 and 27 18 414 disclose longitudinal seals disposed in radial grooves extending along the beam and pressed against the beam by the pressure in the chamber formed between the beam and the inner periphery of the shell. During operation, in all embodiments, the inner periphery of the shell slides along the longitudinal seals, during which time the sealing strips are pressed against the sliding surface (i.e. the inner periphery) by a force proportional to the pressure in the chamber.
Years of experience have shown that these rolls operate in a satisfactory manner as long as the pressure in the chamber is below about 25 bar. This pressure is quite sufficient for the use of the aforementioned rolls in the paper, textile and plastics industries.
If however the pressure in the chamber is raised about 25 bar, the friction between the seals and the coacting surfaces increases to such an extent that considerable power is lost and there is a rapid increase in wear. This is particularly serious because rolls are continuously operating components and replacement of a roll is very expensive and often involves closing down an entire production line.
If however rolls of the kind in question are used for processing metals, higher specific pressures are necessary and result in higher pressures in the chamber.
Admittedly it is known in principle from "Melliand Textilberichte" 8/53 (1972), pages 935-940 to use "floating rolls" as described above in the steel industry. In practice, however, additional special constructions are required for this purpose, owing to the higher pressures.